The primary wear out mechanism for spark plugs in combustion engines is the failure of the electrodes due to service in oxidizing conditions at elevated temperatures with high sparking voltages. Precious metal alloys that are typically of a high percentage of platinum content are used to resist erosion caused by the previously mentioned mechanisms. For the side electrode application where the thermal stresses are more severe, the platinum alloy should include metals that help reduce thermal stress on the weld junction between the precious metal and the nickel alloy base electrode. Current platinum alloys have 10% nickel to better match the coefficient of thermal expansion (CTE) of the nickel base electrode that the platinum enhancement is welded onto. Over the last few years platinum prices have increased as much as 100%.
Accordingly, it is desirable to provide a lower cost yet durable platinum alloy for spark plug electrodes.